Downy Mildew

fungus

Various (Peronosporaceae)

Water mold causing angular yellow leaf spots with fuzzy growth underneath. Different organism from powdery mildew.

Identification

Yellow angular spots on upper leaf surface (bounded by veins). Purple-gray fuzzy growth on leaf undersides in humid conditions.

Leaf yellowing and necrosis. Defoliation. Reduced yield. Can kill lettuce and basil crops rapidly.

Copper fungicide (preventive). Remove infected leaves. Improve air circulation. Avoid overhead irrigation.

Mancozeb. Metalaxyl (specific to oomycetes). Phosphorous acid.

Resistant varieties. Morning watering. Wide plant spacing. Remove crop debris. Basil: use resistant varieties like Prospera.

Data confidence: medium | Source: curated_ipm